Nutritional Evaluation, Characterization and Antioxidant Activity of Radix Isatidis Protein Hydrolysates under Simulated Gastrointestinal Digestion

Abstract

In this study, the antioxidant activities of alcalase-treated Radix Isatidis protein hydrolysates (RIPH) were compared during a two-stage gastrointestinal (GI) digestion in vitro. Compared with the blank, the enzymatic breakdown of the GI digests increased their 1,1-diphenyl-2-picrylhydrazyl (DPPH) (1.2-fold increase), hydroxyl (1.9-fold increase), superoxide anion (5.6-fold increase) in the radical scavenging activities and the reducing power (4.0-fold increase). The investigated items of RIPH consisted of the degrees of hydrolysis (DH), the compositions of amino acid, the nutritional parameters and the molecular weight distributions (MWD). The analysis of amino acid compositions of RIPH showed that essential amino acids such as isoleucine, threonine, tryptophan, valine and histidine took a high portion. The final Radix Isatidis protein hydrolysate digests (FRIPHD) contained the free amino acids of about 29.4%. Results from this study showed that RIPH is a good source of natural antioxidants that the formed peptides can resist physiological digestion in GI digestive system.